Reversible digging tooth with three cutting edges



Jan. 31, 1967 I w TROEPPL ETAL 3,300,883

REVERSIBLE DIGGING TOOTH WITH THREE CUTTING EDGES Filed Oct. 21, 1965INVENTORS fl/LL/IM M 72 05;; 6:94;; A. parses! ,4rrazvi/ United StatesPatent 3,300,883 REVERSIBLE DIGGING TOOTH WITH THREE CUTTING EDGESWilliam M. Troeppl, Santa Clara, and Gerald A. Petersen, Sunnyvale,Calif., assignors, by direct and mesne assignments, of one-half to saidPetersen, and one-half to Anita E. Petersen, Saratoga, Calif.

Filed Oct. 21, 1963, Ser. No. 317,541 6 Claims. (Cl. 37-142) Thisinvention relates to a new and improved reversible digging tooth withribs on the tooth surface to confine wear so that the tooth assumes apredetermined shape as it is used. Reference is made to US. Patents Nos.2,877,574, 2,952,085 and 2,968,880 on which the present invention is animprovement.

A particular feature of the present invention is the formation on thetop and bottom forwardly-converging distal surfaces of the tooth ofreinforcing ribs, extending longitudinally adjacent but spaced inwardlyfrom the side margins of the tooth. It will be understood that as adigging tooth is subjected to use, the forward edge of the tooth tendsto be worn away. Further, when the tooth is used on an auger, the sideedges of the tooth are like wise subjected to wear by reason of therotary motion of the tooth, particularly when such tooth is held in anauger head of the type shown in Patent No. 2,578,014. Use of ribs on thetop and bottom surfaces of the tooth, which in practical effect compriseenlargements of the vertical cross-section of the tooth, retard wear ofthe toot-h at the cutting edge vicinal the forward end of the rib. Thepresent invention locates such reinforcing ribs in preferred locationsso as to obtain a beneficial effect from the inherent wear of the tooth.

Accordingly, as the tooth formed as hereinbefore mentioned wears, a pairof prongs forms at the leading edge of the tooth, which prongs performan efiective digging function. Such prongs are spaced inwardly from theside edges of the tooth and are spaced apart with a thinnercross-section of the tooth between the two prongs. Further, by reason ofthe thinness of the tooth between the reinforcing edge and the sidemargin, a cutting blade is in practical effect formed along the sideedges of the tooth which is particularly effective in digging sideclearance in an auger.

A feature and advantage of the present invention is that the location ofthe ribs, as hereinbefore explained, prolongs the life of the tooth andalso, after the tooth wears, makes its digging action more effective.

A still further feature of the invention is the fact that reversal ofthe tooth prolongs the life of the tooth and reduces the frequency ofsharpening, grinding or replacing the same without diminishing theeffectiveness of the digging action of the tooth. The tooth isparticularly suitable for use in boring a hole with an auger of the typeshown in Patent No. 2,578,014, where the tooth is slanted at an angle.The front edge of the tooth performs a major portion of the cuttingaction. However, since the blade of the tooth is rectangular in plan, aportion of the outside side edge as well as a portion of the inside sideedge also perform digging action because such edge portions travelslightly radially outward or inward, respectively, as the toothrevolves. For greatest eificiency in digging action the edges which outshould be thin, but for practical considerations of strength the edgesmust be reinforced. A principal feature of the present invention is theprovision of ribs extending longitudinally spaced inwardly from the sideedges. Such ribs permit thin front and side cutting edges without unduesacrifice of strength. At the same time, any adverse effect on boringcaused by the ribs is compensated for to a substantial extent by3,300,383 Patented Jan. 31, 1967 the improved boring accomplished by thethin edges, and this is particularly true after the tooth has beenreversed.

Other objects of the present invention will become apparent upon readingthe following specification and referring to the accompanying drawingsin which similar characters of reference represent corresponding partsin each of the several views.

In the drawings:

FIG. 1 is a fragmentary view of a tooth in accordance with thisinvention viewed from the side, together with a portion of the toothholding structure.

FIG. 2 is a cross-sectional view, taken substantially along the line 2-2of FIG. 1.

FIG. 3 is a top plan view of the tooth, in new condition.

FIG. 4 is a sectional view taken substantially along the line 44 of FIG.3.

FIG. 5 is a fragmentary view similar to FIG. 3, showing the tooth afterit has worn partially.

FIG. 6 is a sectional view along line 6.--6 of FIG. 5 showing the toothafter wear.

As has heretofore been mentioned, the present invention is animprovement over Patents Nos. 2,877,574, 2,952,085 and 2,968,880, whichsaid patents show various means for retaining a tooth of this type in aholder. Such a holder may be formed integrally with or attached to adigging implement, such as auger, trencher, or other excavating machine.

In the accompanying drawings, the tooth 11 is shown held in a shank 12,or tooth holder, by means similar to that used and described in PatentNo. 2,968,880 and not herein illustrated or described in detail. Tooth11, at its proximal end, has substantially parallel, reversible top andbottom faces 13, 14, and substantially vertical side edges 16. The rearend 17 of the tooth is essentially square and forwardly of the rear endis a central slot 18, having substantially parallel edges 19 which aretransverse to top and bottom faces 13, 14, to provide a pair of proximalprongs 21 each of which is preferably rectangular in transversecross-section. Prongs 17 assist in holding tooth 11 in holder 12. Slot18 extends forwardly to a forward transverse terminus 22, which isspaced forwardly of the rear end of the toot-h approximately onehalf thelength of said tooth.

Forwardly of slot '18, the top and bottom distal faces 26, 27, convergeforwardly to a blunt transverse cutting edge 25 which, in the initialcondition of the tooth, extends straight across the entire width of thetooth (see particularly FIG. 3). Intermediate surfaces 26, 27 and prongsurfaces 13, 14 are top and bottom blending surfaces 28, 29,respectively, which are curved and merge the substantially parallel topand bottom surfaces 13, 14 into the narrower converging surfaces 26, 27.

As a feature of the present invention, there is formed on both the topand bottom surfaces on either side of the tooth alongitudinally-extending upwardly-protruding rib 31, which originates atabout the forward end 22 of slot 18 and has its inner edge asapproximately a forward projection of wall 19 of slot 18, and has itsopposite or outer edge 33 parallel to inner edge 32 at the distal end ofthe tooth merging in a curved surface 34 to the outside edge 16 of thetooth. It will be noted that the outside edge 33 of rib 31 is spacedinwardly from the outside 16 of the tooth a distance about equal to thewidth of the tooth and the ribs 31 are spaced apart about four times thewidth of the ribs-which is also about one-half the overall width of thedistal end of the tooth.

The thickness of ribs 31 diminishes from a maximum at their originationsto a minimum at end 25. The maximum thickness of each rib is about 7 andthe maximum thickness between faces 13, 14, about (These dimensionsbeing for a tooth width of two inches.)

With special attention to FIG. 2 of the accompanying drawings, it willbe seen that the portions 36 on either side of the tooth, outside ofribs 31, are thinner than the contrasting portion 37 between the ribs31, being about /s thick.

Directing attention now to FIG. 5, it will be seen that after the toothhas been used as in an auger, wear occurs. Thus in the center of theforward end of the tooth, as indicated by reference numeral 41, theleading edge curves backwardly between the ribs 31, and to either sideof the ribs 31, as indicated by reference numeral 42, the sides are wornaway in a diagonal line. This forms two prongs 43 at the front of thetooth which perform an efiective digging action. It will further beunderstood that the edge 42 is relatively shar-p by reason of thewearing away of the thin portion 36 on either side edge of the tooth.

The resultant tooth having forwardly extending prongs 43 may be usedeffectively and efiiciently to prolong the life of the tooth. Further,as the ribs 31 wear, the tooth may be inverted and reused.

What is claimed is:

1. A tooth formed of a unitary piece of material comprising a proximalportion formed to provide means for attachment to a cooperatingtooth-holder and a distal portion, said distal portion having a thintransverse front cutting edge, thin side edges extending rearwardly ofsaid front cutting edge and forwardly converging top and bottom faces,said faces inwardly from each said side edge being spaced apart fromeach other a distance substantially greater than the thickness of saidside edges, said side edges being substantially of the same thickness assaid front cutting edge, said top and bottom faces being formed withlongitudinal ribs and at the center of said tooth said faces beingspaced apart from each other a lesser distance than at said ribs.

2. A tooth according to claim 1 in which each said rib has a Width equalto about one-eighth the width of said tooth and the outer edge of saidrib is spaced inwardly from the adjacent side edge of said tooth aboutoneeighth the width of said tooth.

3. A tooth according to claim 1 in which, spaced approximately halfwayup said distal portion, the thickness of said tooth throughcorresponding ribs on the top and bottom surfaces is about five-thirdsthe thickness through the tooth intermediate said ribs.

4. A tooth according to claim 1 in which the thickness of said toothoutside said ribs is less than the thickness intermediate said ribs.

5. A tooth according to claim 1 in which said proximal portion comprisesa pair of prongs each substantially rectangular in cross-section anddivided by a slot extending forward from the proximal end of said tooth,the outside edges of said distal portion being substantiallycontinuations of the parallel outside edges of said prongs.

6. A tooth according to claim 5 in which the thickness of said prongs isgreater than the maximum thickness of said distal portion intermediatesaid ribs and approximately equal to the maximum thickness of said tooththrough said ribs.

References Cited by the Examiner UNITED STATES PATENTS 1,395,048 10/1921McKee 37--1 42 2,623,309 12/1952 Frye 37-142 2,952,085 9/1960 Petersen413 X 3,149,679 9/1964 Johnson et al. 172-713 3,203,488 8/1965 Eastwood37-442 X ABRAHAM G. STONE, Primary Examiner.

WILLIAM A. SMITH HI, Examiner.

1. A TOOTH FORMED OF A UNITARY PIECE OF MATERIAL COMPRISING A PROXIMALPORTION FORMED TO PROVIDE MEANS FOR ATTACHMENT TO A COOPERATINGTOOTH-HOLDER AND A DISTAL PORTION, SAID DISTAL PORTION HAVING A THINTRANSVERSE FRONT CUTTING EDGE, THIN SIDE EDGES EXTENDING REARWARDLY OFSAID FRONT CUTTING EDGE AND FORWARDLY CONVERGING TOP AND BOTTOM FACES,SAID FACES INWARDLY FROM EACH SAID SIDE EDGE BEING SPACED APART FROMEACH OTHER A DISTANCE SUBSTAN-